A smart defensive player knows when to backcheck the puck carrier and when to backcheck to cover an open player.

Hockey has no greater test of your heart and intensity than your willingness to backcheck, particularly at the end of a sustained attack when the other team has suddenly come up with the puck and you are feeling exhausted.

2007 March 26, Lynn Zinser, “Rangers Stay Cool in Another Pressure-Filled Win”, in New York Times[1]:

It’s been a real team effort, a commitment to defense and backchecking by everybody.